Optical devices are used as various illuminating devices or displays. Generally, it is necessary for the optical device to have a joining structure that joins different materials such as terminals and interconnections for transmission of an electrical signal that drives the optical element. For example, the organic EL element, which is an example of an optical element, includes a transparent electrode, another electrode that is disposed to face the transparent electrode, and an organic layer that is interposed between the electrodes. As a technology relating to the organic EL element, for example, there is a technology which is described in Patent Document 1.
Patent Document 1 discloses a light-emitting element including an electrode that includes a metal line formed in a linear shape, and a polymer line that is a layered structure of a conductive polymer covering an upper surface and a lateral surface of the metal line.
In addition, Patent Document 2 also discloses a technology of constructing an electrode by using a conductive polymer. Patent Document 2 discloses a semiconductor device which uses a low-resistance portion of an organic conductive material film in which the low-resistance portion and a high-resistance portion are formed through irradiation of energy rays, as an electrode or an ohmic contact.